Two things I think this game needs
One is Invincibility frames upon getting hit, atleast by the same enemy.
The other I'd say is an option to enable autofire on your primary weapon.
Also in my opinion the jetpack shouldn't use up all its fuel when you let go off it for flying for just a short bit of time.
Another thing bothering me is the lack of variety in the playspace, a lot of games like these have a randomly generated enviornment as to not make every run the same.
Otherwise I think it's a pretty good game.